Ehrlichia canis
Classification
Higher order taxa Bacteria; Proteobacteria; Alphaproteobacteria; Ricketsiales; Anaplasmataceae; Ehrlichia
Genus Ehrlichia Canis
Description and significance
Ehrlichia Canis is a rod shaped, "small obligately intracellular, tick-transmitted, gram-negative, {alpha}-proteobacterium" transmitted by the brown dog tick, Rhipicephalus sanguineus. It resides as a microcolony inside a "membrane-lined intracellular vacuole, primarily within monocytes and macrophages of mammalian hosts". E. canis was first discovered in Algeria in 1935 and has now been known to have spread all over the United States, Europe, South America, and Asia. Infected dogs that are not treated can become asymptomatic carriers of the disease for years and eventually die from massive hemhorrage. Little is understood about the pathogenesis of canine and human ehrlichioses so the E. canis genome has been sequenced for more information critical for the development of effective vaccines. The complete genome was sequenced by the Joint Genome Institute by using a combination of 3-kb, 8-kb, and fosmid (40-kb) libraries.
Genome Structure
The genome of E. canis consists of a single, circular chromosome. Its genome is smaller than other ehrlichiae.
Cell structure and metabolism
E. canis is an aerobic organism that is unable to use glucose or fructose as a carbon or energy source. The main energy and carbon source is amino acids. Because it is a persistent infection, E. canis "has mechanisms that allow it to evade host defenses". It lacks peptidoglycan and lipopolysaccharides, which are "major pathogen-associated molecular patterns found in the cell walls of other gram-negative bacteria". These fundamental structural and composition differences in cell walls may be not be "recognized by innate pattern recognition receptors such as Toll-like receptors 2 and 4".
